A Preliminary Investigation On Biocontrol And Growth Promotion By Endophytic Chaetomium Spirale ND35

The endophytic fungus Chaetomium spirale ND35 was isolated from healthy plants Populus tomentosa. The biological control activities and plant growth-promoting abilities of ND35 on tomato, bean and cucumber were studied in laboratory chamber, greenhouse and field. The investigations of the biocontrol mechanisms of ND35 will provide the theory foundations on exploitation of this new strain in agriculture in the future.The action of strain ND35 was preliminary investigated by the confronting bioassay on PDA plates and light microscopy observation. Strain ND35 exhibited different inhibitory effects on the mycelial growth of four pathogenic fungi , Botrytis cinerea, Alternaria solani, Pythium aphanidermatum and Rhizoctonia solani. The growth inhibition ratio was 54.0﹪, 13.5﹪,55.1﹪and 40.9﹪respectively. Furthermore, stain ND35 showed mycoparasitic phenomena, such as overgrowth in pathogen colonies and coiling around the hyphae of the pathogens.After being inoculated on the seedling roots of cucumber, tomato and bean in greenhouse, the mycelia of strain ND35 could colonize in roots in three days, spread into stems and leaves in seven days in greenhouse. Another experiment also showed the resemble results. The mycelia of strain ND35 could infest into the embryonic roots of cucumber and tomato in forty-eight hours to seventy-two hours under the sterilized conditions. The microscopy observation showed the mycelia expanded into the protoplast after their penetration of cell walls and membranes of the embryonic roots.The strain ND35 could promote the growth of the tomato plants after the colonization in them. The seedling hight, root length, fresh weight of seedling and root had more higher index than the control. After examining some photosynthesis index of the third and the forth leaves of the seedlings pre-treated with strain ND35 and non-treated control in their midanaphase, such as net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular CO2 concentration(Ci), we found the strain ND35 could enhance photosynthesis performances of the tomato seedlings.The field experiments indicated that strain ND35 could enhance tomato productivities. The quantities of developing flowers, nondeciduous fruits and the single plant productivity of the treated plants were 75.8﹪, 22.7﹪and 14.5﹪higher than the control respectively.In greenhouse, the pot biocontrol experiment showed that strain ND35 had good control effects on bean hypocotyl rot caused by R. solani and cucumber damping-off caused by P. aphanidermatum. Strain ND35 and Rhizoctonia solani were inoculated on the bean seedling roots simultaneously. The disease index decreased from 51.7 to 25.4. The control efficiency was 50.9﹪. The cucumber seedlings which were pre-treated with strain ND35 reduced the disease incidence from 68.9% to 13.3%. Its control efficiency was 80.7﹪.Another pot experiment in greenhouse showed that strain ND35 stimulated the tomato seedlings getting the disease resistance abilities against tomato gray mold caused by Botrytis cinerea. The best control effects on leaves appeared after the inoculation of strain ND35 on the roots from three days to ten days. The control efficiency was 22.9﹪~35.6﹪. Moreover, the enzyme activities in leaves associated with defense response were increased, including PAL, POD and PPO.